Thai  stocks  slid, dragging the benchmark index down the most in Asia, on concern floods and a potential U.S. government shutdown will hurt economic growth.

The  SET Index (SET)  sank 2.1 percent to 1,388.04 at the break in Bangkok, heading for the lowest close since Sept. 9.  Siam Cement Pcl (SCC)  dropped 3.6 percent, the biggest contributor to losses.  PTT Exploration & Production Pcl (PTTEP)  fell 2.6 percent after  crude oilslumped in New York.

Floods have killed 22 people and affected 25 provinces, the Department of Disaster Prevention and Mitigation said on its website. Director of the National Disaster Warning Center Somsak Khaosuwan said the situation was ?completely different? from 2011, when the worst floods in 70 years shuttered hundreds of factories including those of Honda Motor Co. U.S. Congress has just one day to end a stalemate that raises the risk of the first government shutdown in 17 years.

There?s concern over the impact of the current flooding on the economy, Rakpong Chaisuparakul, an investment strategist at KGI Securities (Thailand) Pcl, said by phone from Bangkok. ?Anxiety over a possible U.S. government shutdown has also affected stocks inThailand.??

Overseas investors sold a net $111.5 million of Thai shares on Sept. 27, the fifth straight day of net sales,  data  compiled by Bloomberg show. The SET has gained 7.2 percent this month, paring its quarterly decline to 4.4 percent.